In a mobile communication system which enables mobile communication terminals like cellular phones to communicate with each other, there has been proposed a technology of notifying information indicating an importance level set by a call-transmitting user (hereinafter, “transmitter”) together with a transmission-originating phone number to a call-receiving user (hereinafter, “recipient”). For example, according to a mobile communication terminal disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2001-103551, when a transmitter enters a phone number that the transmitter wishes to call, a security code and a priority information identification code are entered following to a transmission-destination phone number. Accordingly, a calling setting message having calling control information to which information element like priority information is added is transmitted over a communication network.
However, such importance setting function of a mobile communication terminal may be abused. For example, some traders carrying out sales, soliciting and the like may make a phone call while setting the importance level high in order to attempt a recipient to answer the phone. If the importance level is always set high when the recipient receives a call which is not important to the recipient, the recipient stops believing the set importance. Hence, if the importance setting level is abused, the function of the importance level setting may not be effectively used. Therefore, there is a demand for a technology which suppresses any abusing of importance level setting of a telephone call subject.